Light source



Ap 9, 1940. s. SPERTI LIGHT SOURCE Original Filed Sept. 24, 1931 gwomtw Patented Apr. 9, 1940 UNITED STATES uon'r sormca George Spertl, Covinrton, Ky., assignor to Sperti Lamp Corporation, New York, N. Y., a corporation oi Delaware Application September 24, 1931, Serial No. 584.907

Renewed June 29, 1937 14 Claims. (Cl. 1"l81) This invention relates to light sources and" particularly to light sources which combine both visible and ultra-violet radiation to produce a spectrum closely resembling that of natural sun- 5 light. This application is a continuation in part of my prior application Serial No. 368,249 filed June 4, 1929.

The importance of sunlight as a therapeutic agent has been recognized for a long time and recently it has been appreciated that the most effective part of the sun's radiations for therapeutic purposes lies in the ultra-violet region of the spectrum. Sunlight under good conditions contains radiations as short as about 2950 Angstrom units and radiations between this lower wave length limit and wave lengths in the p 3100 to 3200 Angstrom unitsneighborhood of have great therapeutic value. Appreciation of this fact has led to the use of artificial sources of ultra-violet light for therapeutic purposes, particularly the mercury arc lamp. Therapeutic lamps of this type, however, are not in general adapted for general illumination because they do not contain suificient quantities of the yellow and red rays of the visible spectrum. On the other hand, the usual illumination sources such as incandescent tungsten lamps are deficient in.

the valuable ultra-violet radiations both because the short wave lengths are not produced at ordinary filament temperatures and because ordinary glass bulbs do not. transmit the desired short radiations. It is accordingly desirable to produce a light source adapted for general illumination purposes and having a spectral energy distribution throughout the visible and ultra-violet regions thatis substantially equivalent to natural sunlight.

The most convenient source of ultra-violet radiation is anarc of mercury or other vapor, 0 but the mercury arc provides a bluish white light which is rich invultra-violet radiation but deficient in the yellow and red radiations oi the visible spectrum and other vapor arcs are similarlyv deficient. It has therefore been proposed to supplement these vapor arcs, as for example to supplement the mercury arc with yellow and red rays, by means such as the combination of an incandescent filament therewith or the use of a tungsten or other arc in an atmosphere of mercury or other vapor together with an incandescent fllament. These devices while producing in certain cases light of approximately the character desired have been open to objection because among other reasons they are not adapted to be operated at normal voltages and currents found in the usual house lighting systems. When operated at such voltages, sputtering of the fllamentary material, burning out of the filament and blackening of the lamp bulb take place very quickly and difliculties may also beencountered in starting the arc. Consequently the field of use of such lamps has heretofore been restricted to special installations and uses where transformers and other auxiliary equipment external to the lamp itself are employed.

One of the objects of this invention is to provide a light source combining both visible and ultra-violet radiation and closely resembling natural sunlight in character, quality and energy distribution, which can be used in an ordinary lamp socket without additional equipment and is adapted for all of the uses to which the ordinary incandescent filament lamp can be put.

Another object is to provide a light source combining both ultra-violet and visible radiation which can be operated economically and without deterioration at normal house lighting voltages and currents.

A further object is to provide a light source embodying an incandescent element and an arcin mercury or other vapor which can be operated at normal house voltages-without sputtering or blackening the walls of the lamp or destruction of the filament.

Another object is to provide an inexpensive but eflicient electric lamp for general house illumination which emits radiations in both the visible and ultra-violet regions of the spectrum corresponding in quality with natural sunlight.

With the above objects in view, the invention includes the combination of a source of visible light and a-source of ultra-violet light in a single bulb of glass or othermaterial translucent to the desired visible and ultra-violet radiations.

The visible radiation is provided by an incandescent member of suitable material, and the ultraviolet radiation by an arc in mercury or other vapor, the two sources being arranged as hereinafter described so that the lamp can replace the ordinary incandescent lamp for all purposes. As materials for electrodes between which the arc is caused to strike, metals and their oxides of the rare earth metal group such as zirconium oxide, or coatingsof such or other suitable oxides, may be employed, some of such oxides being second'class conductors or in other words being non-conductors of very high resistance when cold-but becoming good conductors and having low resistance on heating. These materials when cold adsorb the mercury or other vapor in the bulb of the lamp, and on being heated, give off the vapor so that the arc strikes. Also it is possible that electronic bombardment of the vaporizable material will contribute to the ionization. Other suitable materials are oxidecoated tungsten, platinum, etc. The adsorbing and emitting properties of these materials are such that a pool of free mercury is unnecessary.

For heating the electrodes and also'to estab lish a potential difference therebetween to support the arc, the electrodes are connected by resistance means which embody a resistance heater for the electrodes and an element which incandesces and emits visible radiation, together with means whereby the resistance means and are are rendered stable and permanent in the presence of each other when the lamp is operated at 'the desired voltage. Said resistance means may comprise a filament or filaments of tungsten, graphitic or carbon substances, or any other suitable material, suitably enclosed as by a tube so as to be kept out of contact with the mercury or other vapor in the bulb. The filament or its enclosure is adapted to incandesce and constitute a source of visible radiations, and to this end the enclosing tube may be of a material such as zirconium oxide which itself radiates visible light rich in the red and yellow rays of the spectrum on being heated. Obviously, if the filament itself is to constitute the source of visible light, the enclosing tube will be translucent. aheater for the electrodes and the incandescent element, but it will be understood that these functions may be accomplished by any suitable arrangement of filaments. The voltage drop between the ends of the resistance means is applied across the electrodes to support the arc so that the arc-sustaining current is in parallel with the current through the resistance means. Sputtering or disintegration of the resistance materials such as tungsten and the like, blackening of the lamp bulb, and destruction of the resistance "element or filament are prevented since the resistance materials are enclosed and kept out of contact with the mercury or other vapor. Hence the lamp can be operated successfully and efliciently at 110 volts or more with a potential difierence across the arc of 90 to 100 volts or less if desired.

One embodiment of the invention is illustrated in the accompanying drawing which shows diagrammatically one form of lamp embodying the above features, but it is to be expressly understood that the drawing is for purposes of illustration only and is not to be construed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

The lamp may have any suitable or desired shape like the ordinary incandescent lamp. As shown,. the bulb of the lamp is of conventional form and is provided with the usual or any suitable base 2 which is of the screw type. The lamp envelope or bulb I is of suitable material translucent to ultra-violet as well as to visible radiation such as quartz glass, although any other known glass which transmits the desired ultra-violet radiations can be employed instead of quartz. Various ultra-violet transmitting glasses are known which have different transmission characteristics, as for example, glasses which do not transmit radiations shorter than about 3000 Angstrom units, and any such glass maybe employed which transmits radiations of Thus the same filament may serve as the desired wave lengths. The lamp is also provided with the usual standard 3 of suitable glass or other material throughwhich leads 4 and 5 are led into the lamp bulb. k-.-

In the form shown, the electrodes forthe are are formed of zirconium oxide and for convenience a zirconium oxide tube is used, the end portions of the tube constituting the electrodes and the tube being employed as an enclosure for the filament or resistance means. As shown in the drawing, a tube 6 of zirconium oxide is bent in the general form of a U and contains a graphitic or tungsten filament indicated diagrammatically at l, the tube being secured in any suitable way to the standard 3 and the leads 4 and 5 being connectedto the ends of the U so that they make electrical contact both with the zirconium oxide tube and with the enclosed filament. I

Bulb 1 is preferably evacuated and contains a quantity of mercury or other suitable material indicated graphically at 8. When current'is applied to the lamp, it passes in series through the lead 4, filament I, and lead 5. The filament and the tube 6 rapidly heat up and become incandescent, the tube thereby providing a source of visible light. The tube 6 becomes a conductor on heating, and a potential difierence is established between the opposite end portions of the tube by virtue of the resistance drop through the filament and tube. As themercury or other substance in the tube ionizes, an arc strikes between the electrodes formed by the end portions of the tube 6, providing a source of ultra-violet radiation. The radiation from the arc can be controlled in proportion to the visible radiation by controlling the arc current so that the light from the lamp is substantially the same in quality as natural sunlight. It will be understood that the mercury or other material is adsorbed by the zirconium oxide on cooling and re-emitted when the lamp is next used.

It will be seen that the lamp embodies resistance means connected in series with theleads 4 and 5 and constituting both means for heating the arc electrodes and means for emitting visible radiations. The electrodes have impressed on them the potential drop through the resistance means, and the arc-sustaining current is in parallel with the current through the resistance means. At the same time the heating source is isolated from the arc and none of the filamentary material is exposed so that no sputtering or blackening of the lamp bulb or premature destruction of the filament results on use of the lamp. Accordingly a lamp of this kind can be operated at 110 volts without damage and hence can be substituted for the ordinary incandescent lamp at will. The illumination provided by the lamp is of white color closely resembling sunlight in quality.

It will be understood that the invention is not limited to the form illustrated and described, but is capable of considerable variation. For example, the enclosure for the filament 1 need not be in the form of a tube, and moreover, the tube 6 need not be formed of the electrode material and the electrodes may be separate from the tube and connected with the resistance means in any suitable way. Moreover, the oxide-coated electrodes may be separate from main electrodes of tungsten or the like, the oxide-coated electrodes serving to start the are which then transfers to the main electrodes. The size and shape of the bulb and the type of base may be varied as desired. Reference is therefore to be had to the appended claims for a definition of the limits or the invention.

What is claimed is:

1. A lamp comprising a bulb translucent to visible and ultra-violet radiation, a pair of leads, a filament connected in series between said leads, means within said bulb for enclosing said filament, said means providing electrode means in electrical connection with said filament whereby the potential drop therethrough is impressed across said electrode, means and a quantity of .ionizable material in said bulb which radiates in the ultra-violet region of the spectrum, said filament enclosing means shielding the filament from contact with said ionizable material.

2. A lamp comprising a bulb translucent to visible and ultra-violet radiation, a pair of leads extending within said bulb, a tube mounted within said bulb, a filament enclosed within said tube and connected in series across said leads, the end portions of said tube constituting arc electrodes and having electrical connection with theends of said filament whereby the potential drop through the filament is impressed across the electrodes, and a quantity of ionizable material in said bulb which radiates in the ultra-violet region of the spectrum.

3. A light source comprising a light transmitting vessel, a tube of zirconium oxide fused at its ends to said vessel, a heating means within said tube, and terminal connections to the ends of said heating means and said tube connecting said elements in parallel with one another, said light transmitting vessel being evacuated and containing a quantity of ionizable material.

4. A lamp comprising a bulb translucent to visible and ultra-violet radiation, a pair of leads extending within said bulb, a U-shaped tube mounted within said bulb, at least the end portions of said tube being of zirconium oxide and receiving the inner ends of said leads, a filament wholly enclosed within said tube and connected in series with said leads, the end portions of said tube constituting electrodes and having electrical connection with the ends of said filament whereby the potential drop therethrough is impressed across the electrodes, and a quantity of ionizable material in said bulb which radiates in the ultraviolet region of the spectrum, the enclosure of said filament within said tube shielding the former from contact with the are formed between the electrodes.

5. An electric lamp adapted to provide both visible and ultra-violet radiation and comprising an outer envelope capable of transmitting freely both visible and ultra-violet radiation down to the short wave length limit of natural sunlight,- a pair of terminals for said lamp and connected by a closed circuit including a hot filament, an ionizable medium, and means in said lamp separating said filament from said ionizable medium and cooperating with said filament to form a source of visible radiation, said means also comprising solid electrode means connected to and electrically heated by said closed circuit to establish an arc in said ionizable medium.

6. An electric lamp embodying incandescent and are light sources and comprising an outer envelope capable of transmitting radiation from both sources, a screw-type base having two terminals, an ionizable medium, a hot filament connected in a closed circuit across said terminals, 9. press, and means mounted on said press for separating said hot filament from said ionizable medium and comprising solid electrode means for the are, said electrode means being connected to said closed circuit and electrically heated thereby.

7. A light source comprising a vessel transmitting both visible and ultra-violet light, a tube or zirconium oxide mounted within and fused at its ends to a portion of said vessel, a pair of terminals for said light source'having electrical connection with the ends of said tube, a quantity of ionizable material in said vessel whereby an arc is formed therein by the potential diflerence between the ends of said tube, and a heating filament enclosed within said tube and shielded thereby from contact with the arc atmosphere. 1

8. An electric lamp adapted to produce both visible and ultra-violet radiation and having a single pair of terminals, a permanent closed circuit including a filament and connected across said terminals, and means for establishing a gaseous discharge comprising an ionizable medium radiating in the ultra-violet region of the spectrum and a refractory oxide electron-emitting material subject to heat from said circuit for causing ionization of said medium whereby said discharge is established between points of diflerent potential in said circuit.

9. An electric lamp of the type having two sources of light therein, one an incandescent source and the other a gaseous discharge, said lamp comprising a bulb containing an ionizable medium and having a single pair of terminals, permanently closed circuit connections between said terminals adapted to incandesce on passage of current and including a heating element, and a refractory oxide electron-emitting material heated by said element to cause ionization of said medium, said discharge being established and maintained between points of difierent potential in said closed circuit.

10. An electric lamp of the type having a single pair of terminals and an incandescent means and a gaseous discharge means both connected for energization to said two terminals, said lamp comprising a closed circuit permanently connected across said terminals and including filament means, means for enclosing said filament means from said discharge, said enclosing means comprising at least in part a refractory electronemitting oxide heated by said filament means, and an ionizable medium capable of being ionized on heating said oxide, said discharge being established and maintained between points of different potential in said circuit.

11. An electric lamp of the type having a single pair of terminals and an incandescent means and a gaseous discharge means both connected for energization to said two terminals, said lamp comprising means forming a closed circuit permanently connected between said terminals and adapted to incandesce on passage of current, said circuit means including at least one filament, means for enclosing the filamentary portion of said circuit from said discharge comprising at least in part a refractory electron-emitting oxide heated by said filament, and an ionizable medium capable of ionization on heating said oxide to establish the discharge, said discharge being established and maintained between points of different potential in said circuit.

12. An electric lamp device comprising a container, a gaseous filling therein, a filament sea-led therein, said filament having sections connected in series and angularly disposed with respect to I each other, said filament comprising a high melt- 76 ing point metal and an electron emissive material for emitting electrons, said electrons exciting said gaseous filling in an electric discharge path between said sections as electrodes, said discharge path being electrically parallel to the conduction path through said filament.

13. An electric lamp ultra-violet generating device comprising a container, a gaseous filling therein, a filament sealed therein, said filament having sections connected in series and angularly disposed with respect to each other, said filament comprising a high melting point metal and an electron emissive material for emitting electrons, said electrons exciting said gaseous filling in an electric discharge path between said sections as electrodes, said discharge path being electrically GEORGE SPER'I'I. 

